1. Field of the Invention
The present invention relates to a surgical seal assembly and, more particularly to a surgical instrument seal assembly which is capable of maintaining a fluid seal around a surgical instrument.
2. Background Description
In certain types of surgery, a cannula is used to provide a passageway into a body cavity so that a surgical instrument may be passed into that cavity. Cannulas are typically elongate rod-like members having a central bore so that a surgical instrument may be passed through the bore. At times, the body cavity will be insufflated by a gas and at all times, the cannula will be subjected to internal body fluids. Therefore, some form of seal assembly is necessary to allow the surgical instrument to pass through the cannula while maintaining sealed integrity around the instrument such that the insufflation gas, the internal body fluids, or both, cannot escape through the cannula.
In conventional devices, such a seal mechanism includes a housing for mounting on the cannula, with the housing having a bore therethrough for passage of the surgical instrument. Two seals are typically located within the housing. The lower housing contains a seal, typically called a duckbill valve that assists in maintaining gases and fluids in place when an instrument is not inserted within the duckbill valve. The duckbill valve is typically formed from flexible material and includes a slit opening that is capable of deflecting upon insertion of the instrument. The upper housing typically includes a valve seal that includes a relative wide access opening and a relatively narrow valve opening. The valve opening can expand to accommodate the surgical instrument and is resilient to form a seal around the instrument upon insertion.
These conventional seals, however, may not adequately seal the instrument during a surgical procedure. Also, the elastomeric material of the valve seal can be damaged by contact with the surgical instrument upon insertion. As a result, seal protectors have been used. The seal protectors are units separate from the valve seal and are disposed intermediate the seal and the surgical instrument. Some seal protectors include complex lever arrangements that may engage and open the valve opening while acting as a barrier between the instrument and the valve seal. Other approaches include the application of rigid plastic leaf-like members in an overlapping, circular array in abutment with the valve seal. The overlapping arrangement allows the leaves to open upon insertion of an instrument. These approaches have been generally costly and complex.
Another problem with conventional devices has been the inability of the valve opening to align with the instrument if the instrument is inserted “off axis” (i.e., out of alignment with the throughbore in the valve seal). Attempts to resolve this problem have resulted in special mounting arrangements for the valve seal where the valve seal is laterally displaceable within a housing holding the valve seal. These solutions have required additional material and can be expensive and complex to implement.
By way of specific example, U.S. Pat. No. 5,147,336 to Antoon shows a trocar with a seal for sealing against surgical instruments of varying diameter to maintain insufflation in the body cavity. The seal has an elastomeric sealing component with a centrally located interior region containing an aperture, and a concentrically located sealing region. The sealing region is composed of an overlaying layer co-molded with an underlying layer. The overlaying layer has a hardness greater than that of the underlying layer. The seal is positioned between upper and lower rigid rings which divides the seal into inner and outer portions. The upper ring has a plurality of prongs which are fitted through the seal and are received in a plurality of receiving holes in the lower ring. The outer portion has a bellows configuration which facilitates the maintenance of a seal during radial motion of surgical instruments which are inserted into and withdrawn from the cannula. The seal assembly of Antoon, however, is difficult and costly to assemble. The seal assembly also requires prongs for support thus adding to the cost of the assembly. It also permits radial motion of the seal which may cause failure of the seal assembly.
The present invention is directed to overcoming one or more of the problems as set forth above.